This application is a continuation-in-part of application Ser. No. 11/026,588, filed Dec. 30, 2004, which is a continuation of application Ser. No. 10/343,723, filed Jan. 31, 2003, now U.S. Pat. No. 6,837,401, which is a U.S. national application based on PCT/US01/29627, filed Sep. 21, 2001, which application claims the priority of provisional application Ser. No. 60/234,488, filed Sep. 22, 2000.
The present invention relates to apparatus and methods for delivery of a fine stream or mist of fluid, preferably, a liquid that has been filtered for removal of particulate contaminants. The invention has particular application to topical anesthetics and refrigerants, hereinafter collectively referred to as vapocoolants. However, the invention is also applicable to substantially any fluid or liquid wherein it is desired to provide a controlled dispensing by stream or mist deposition with regulated positional and/or volumetric delivery. For example, lightweight lubricating oils, wetting agents, cleaning solutions or water may be dispersed in a highly accurate manner. Further, the invention may be applied to a wide range of medical or pharmaceutical preparations, especially those that are topically applied for treatment and/or irrigation.
The apparatus comprises containers, associated valve arrangements and, optionally, filters that provide a long shelf life and maintain delivery characteristics over the shelf life in a manner suitable for pharmaceutical applications. The apparatus operates over a range of pressure commonly encountered in medical applications to provide substantially uniform delivery of liquid or vapocoolant. The apparatus may be constructed to provide either a stream or a mist delivery.
The fluid or liquid may be a self propellant or a propellant may be included in order to pressurize liquids having a vapor pressure insufficient to act as a self propellant. If a separate propellant is used, the propellant may comprise from 5% to 85% of the total liquid in the container.
Suitable propellants include any liquified petroleum gas that vaporizes or boils below room temperature and at a pressure of one atmosphere so that the resulting volume of the gaseous space is 5 to 700 times the volume of the liquid phase. Further, nitrogen or other inert gas may be used as a propellant.
Preferred vapocoolants include ethyl chloride, ethyl chloride-fluorocarbon blends, fluorocarbon fluids and blends of fluorocarbon fluids such as 15% dichlorodifluoromethane and 85% trichloromonofluoromethane. These CHC materials have been replaced in recent years with HFC's or hydro-fluorocarbons. Useful CHC's include 1,1,1,3,3-pentafluoropropane and 1,1,1,2-tetrafluoroethane. Also, non-halogen containing low boiling fluids suitable for topical skin application may be used.
The vapocoolant will typically operate as a self-propellant by providing a suitable pressure for discharge in a vapor space above the liquid supply of vapocoolant. However, an inert gas such as nitrogen may be combined with the vapocoolant to achieve modified discharge characteristics. For convenience, the invention is described hereinafter with particular reference to ethyl chloride commonly referred to as a CHC or chlorofluorocarbon.
Ideally, the containers and associated valve arrangements for ethyl chloride should have a shelf life of three years and meet United States Pharmacopoeia (“USP”) specifications as well as standard aerosol requirements for functionality. As discussed more fully below, certain medical applications also require unique jet stream characteristics over the life of the product. The USP specification for residue in ethyl chloride is 100 ppm.
Heretofore, valve-actuated spray bottles and so-called metal tube containers have been used for delivery of stream and mist flows of vapocoolant. Although such apparatus have provided effective delivery, they have not been entirely satisfactory. More particularly, it has not been possible to economically modify the prior art apparatus to comply with current FDA regulations and commercial production standards. Most notably, undesirable rates of product lost due to valve leakage have been experienced in connection with bottle apparatus. Although the metal tube apparatus provides substantially satisfactory performance, the cost of this delivery system including its threaded valve actuator is not economically attractive.
A current metal can spray system having a button actuated valve has not complied with contaminant or residue standards. That is, the vapocoolant within the spray can contains dissolved or dispersed contaminants believed to result from the solvent action of the vapocoolant on internal polymeric components of the spray can.
The vapocoolants may be used in topical application procedures requiring precise control of the area of skin contacted by the applied stream. For example, treatment of certain myofascial pain syndromes with vapocoolant in combination with stretching procedures may inactivate a trigger point and relieve the patient's pain. A discussion of myofascial pain and myofascial trigger points is provided in the International Rehabilitation Medicine Association monograph, Myofascial Pain Syndrome Due to Trigger Points, by David G. Simons M. D., November 1987, incorporated herein by reference. One specific myofascial therapy is the spray and stretch method of treatment which permits gradual passive stretch of the muscle and inactivation of the trigger point mechanism. To that end, a jet stream of vapocoolant is applied to the skin in one-directional parallel sweeps. Initially, one or two sweeps of spray precede stretch to inhibit the pain and stretch reflexes. The spray of vapocoolant is applied slowly over the entire length of the muscle in the direction of and including the referred pain zone. As described, the stream flow and size characteristics together with precise positioning of the vapocoolant along the muscle being treated is important to achieve inactivation of the trigger point mechanism.
In such procedures, a stream delivery of relatively small dimension is preferred. For example, the diameter of the stream at the valve nozzle may be in the range of several thousandths of an inch, e.g., from about 0.004″ to about 0.015″. Preferably, the delivery flow is stable and the stream configuration is sufficiently maintained to achieve the desired skin contact area with the valve nozzle being positioned up to about 10 or 15 inches from the patient.
In order to achieve such stream stability, the fluid delivery components of the container must not be affected excessively by changes in pressure that occur with change of container orientation during stream application and reduction of the vapocoolant supply within the container during the application life of the container, i.e. the time period within which the container is periodically used before emptied of vapocoolant. Similarly, the button valve itself must receive the flow of vapocoolant from the supply thereof within the container and establish satisfactory fluid flow characteristics prior to the exit of the fluid from the nozzle opening.
The achievement of a fine jet stream requires a nozzle having a highly uniform orifice or opening that is free of dimensional irregularities. For example, a nozzle opening having a diameter of about 0.005″ preferably has a size tolerance of ±0.0005″ along a length in the order of 0.02″.
The reliable provision of such jet stream flows has heretofore been inhibited by the presence of contaminants which may result from in situ formed solid residues or derived from the spray apparatus including the container, valve, actuator and/or flow passage surfaces contacted by the liquid being dispensed, such as a vapocoolant.
Such contaminants may partially block or otherwise sufficiently inhibit or alter flow through the nozzle discharge bore and/or opening so as to prevent the achievement of the desired jet stream. Such contaminants may result from plastic dip tubes and actuator elements that retain manufacturing debris of extremely small size, e.g., elongated flash debris having a 0.0005″ diameter and a 0.010″ length.
The assembly of the valve components has been found to be another source of contaminants. The valve assembly is typically characterized by closely fitted elongated components such as a movable valve member and a spring element mounted within a valve body. Cleaning techniques including washing and vacuum removal are economically undesirable and often not sufficiently reliable.
In addition to contaminate problems, fine streams have been characterized by “after spray” comprising the phenomenon of continued spray after release of the actuator button. Such after spray is undesirable since the user may not continue to direct the spray in the proper direction believing it to be terminated by button release. Generally, after spray is not a problem with nozzle openings exceeding 0.008″ as used, for example, in connection with mist sprays.
Fine stream sprays have also been found to be characterized by undesirable pulsations during spray delivery. This may result in uneven application rates and disconcerting effects upon the person using the spray apparatus.